CS5180 datasheet(21/28 Pages) CIRRUS

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CS5180

APPENDIX A: CIRCUIT APPLICATIONS

Several amplifier circuits have been tested with the

CS5180. Performance at higher frequencies is gen-

erally limited by the operational amplifiers used to

drive the A/D converter.

Figure 12 illustrates a single operational amplifier

circuit which can accept a single-ended ground-ref-

erenced signal and condition it for the input of the

CS5180. The amplifier is AC-coupled to the signal

source. In this circuit the AIN- input to the CS5180

is held at a constant DC value and the AIN+ input

is driven (it is actually overdriven to achieve high

dynamic range, but this sacrifices performance

with regard to distortion). The common mode volt-

age for the CS5180 input should be designed to

stay between 1 V and VREF + 0.25 V when driven

at its AIN+ and AIN- inputs. In Figure 12 the dc

voltage at the AIN- input is set so that when driven

with a 4 Vpp signal on the AIN+ pin, the common

mode voltage remains within the proper range.

Figures 13 and 14 illustrate the performance of the

amplifier of Figure 12 operating with a 4 Vpp input

into the AIN+ input; and with 2 Vpp input into the

AIN+ input respectively.

Figure 15 illustrates an AC-coupled two amplifier

circuit. This circuit gives better performance than

0.15

C0G

10 k

Ω

+15

-15

Ω

AIN-

VREFOUT

CS5180

10 k

Ω

2200 pF

Ω

2200 pF

Ω

10 µF ++

10 µF

0.1 µF

Ω

AIN+

0.1 µF

Figure 12. Single amplifier driving only AIN+, AIN- held at steady dc value

Figure 13. Performance of amplifier of Figure 12 over-

driving AIN+ input to the CS5180 at 4 VPP

Figure 14. Performance of amplifier of Figure 12 with

AIN+ driven at 2 VPP

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